Photoinduced electron transfer from a terrylene dye to TiO2: Quantification of band edge shift effects

A terrylene chromophore exhibiting a high extinction coeff. has been developed as a sensitizer for photovoltaic applications. The photophys. and photochem. properties of the dye were analyzed both exptl. and theor. Terrylene-sensitized nanocryst. TiO2 solar cells yielded good photocurrents providing more than 60% in external quantum efficiency. The photoinduced electron transfer from the dye to TiO2 was found to be very sensitive to conduction band edge shifts in TiO2 induced either by changes in the compn. of the redox electrolyte or by UV illumination. This sensitivity was obsd. in quantum efficiencies for photocurrent generation of terrylene-sensitized solar cells and in photoinduced absorption expts. The conduction band shifts were quantified using charge extn. methods. The obsd. sensitivity of the injection efficiency suggests that photoinduced electron transfer occurs from the relaxed excited state, possibly due to poor electronic coupling between TMIMA excited states and TiO2 conduction band states.